GB1280590A - Systems for controlling the length of a loop of tape in a buffer chamber - Google Patents

Abstract

1280590 Automatic tape control AMPEX CORP 16 Nov 1970 [17 Nov 1969 (3)] 54477/70 Heading G3R Signals proportion to variations of the length of a loop of tape near upper and lower limits between reel and capstan or other drives are applied, with signals representing the direction of movement of the tape on each side of the loop, to a logic circuit controlling the speed of the reel to maintain loop length long or short according to the direction of movement of the tape. In Fig. 1, magnetic tape 10, for recording and reproducing digital information, is stored on reels 12, 14 and moved intermittently in either direction past a record/reproduce head 16 by a capstan 20 driven by a motor 22 controlled by signals from a data processing system. Buffer loops of tape between each reel and the capstan are formed in chambers 30, 32 in which the pressure is reduced by a vacuum source 36. Air bearing guides 34 and small buffer pockets 38, 39 are provided between the buffer loops and the record/reproduce head. If the loop shortens in either chamber so as to expose progressively an upper elongated photo-cell, such as 46, to illumination from lamps 50-52, a signal is applied through an amplifier 60 and summer 82 to proportionally slow down or speed up a motor, such as 28, driving one of the reels so that the length of the loop is restored to the lower limit of the photo-cell. In a similar manner if the loop lengthens to below the top of a lower photocell, such as 48, a signal is applied through an amplifier 64 to restore the loop to the upper limit of the photo-cell. Signals, e.g. from tachometer generators, corresponding to the directions in which the reel and capstan motors are driven, and thus the directions of tape movement on each side of the loop, are applied to a transistor or relay logic circuit such as 62 so that when the bottom of the loop is between the photo-cells and both sides of the loop are moving upward or downward, the appropriate reel drive motor is braked to oppose the movement of the loop. Extreme deviations of the loop are detected by sensors 42, 43 and the reel drive motor current may also be limited.